Variable surface evaporator



1 s. M. ANDERSON VARIABLE SURFACE EVAPQRATOR Filed Dec uuwbom u wk um QM INVENT OR.

6414054. n7. ArvDERsorv ATTORNEY.

Patented Oct. 26, 1943 VARIABLE SURFACE EYAPORATOR Samuel M. Anderson, SharonQltIassQ,assignor to B..F. Sturtevant Company, Boston, Mass.

" Application December 16, 1939, Serial No. 309,599

r y N lllClaim s. This invention relates torefrigeration evaporators and relates more particularly to variable surface evaporators for use with refrigerantcoxm pressors. a

The railroads prefer mechanical refrigeration v I systems for their 'air conditioned passenger cars and they usually specify oversized evaporators for useas air coolers They usually make the contractor responsible for the proper balance between the compressor-condenser equipment and the evaporator, and for the overall performance of the complete equipment. V

With an evaporator too large for the cooling load, excessive back pressure develops so that the compressor cannot deliver its tonnage with- ,1 out excessive pressure. It is desirable therefore,

to adjust the evaporator surface to maintain the proper balance between tonnage, refrigerant temperature, superheat, pressure and'compressor horsepower. This is satisfactorily accomplished in the present invention.

An object of the invention is to adjust the surface of an air cooling, refrigerant evaporator, conformably with load 3 requirements.

Other objects of the invention will be apparent from the following description and from the drawing. g

The invention will now be described with reference to the drawing which illustrates diagrammatically one embodiment of the invention.

, The evaporator 5 has in the embodiment illustrated, .ten horizontal rows.of finned tubes 6, each horizontal row containing nine tubes connected together by the return bends 1. The tubes of the upper five rows are connected by the tubes 8, to the return header 9, and the tubes of the lower five rows are connected by the tubes 10 to a similar header l I.

The upper five rows of tubes are connected by the distributor tubes l2 to the refrigerant dis tributor A. The lower five rows of tubes are connected by the distributor tubes |3 to the refrigerant distributor B. Three tubes back from the right hand end (facingthe drawing) of the evaporator, the upper five rows of tubes are are connected by the distributor tubes IE to the '1 refrigerant distributorD.

The refrigerant distributors A, B, C, and D evaporator 5 at its left hand end ('facingthe drawing) and leave at its right hand end. 1

*The valve" in the refrigerant supply line [8, controls the supply of refrigerant tothe dis tributor A. The similar valve I9, in the refrigerant supply line' 2ll controls thesupply of refrigerant to the distributor B. The" similar valve 21 in the refrigerant supply line 22 controls the supply of refrigerant to the distributor C. The

similar valve 23 in the refrigerant supply line 24 controls the supply of refrigerant to the distributorD. With the valves I1 and I9 open and the valves 2| and23 closed, the evaporator 5 willbefsupplied by the distributors A and B at full capacity; The ten rows of nine tubes per row, ninety tubes in all, will then be supplied with refrigerant. With the valves I 1 and I8 closed and the valves 2| and 23 open, the distributors C and Dwill supply refrigerant to the ten rows of tubes, each row containing seven. tubes, a total'of seventy tubes, the minimum capacity of the evaporator.

With one of the valves A or B open, and the other closed and with one of the valves C or D open and the other closed, five rows of tubes with seventubes per row, plus five rowslof tubes with nine tubes per row, will be served with refrigerant, a total of eighty tubes, the mi d-capacity of the evaporator.

Experience has shown that a railroadco mpanyjspecifying an evaporator for anair conditionedv passenger car would usually specify the maximum capacity evaporator corresponding to the ninety tube one above described, even though it is expected that such an evaporator willfbe too, large for proper operation, at l'eastfor the majority of air conditioned oars. "Since the size of the evaporator for efiicient operation is nicely related to the air conditioning load, compressor capacity, power, refrigerant temperature and pressure, and other factors, the above described variable surface evaporator has been devised for providing the proper evaporator surface for dif? ferent conditions, yet complying with the specifications for over-sized surface.

Although the valves I1, l9, 2] and 23 could be adjusted manually to provide the proper evaporator surface for a given operation condition, in

the embodiment illustrated, a suitable automatic control has been provided as will now be de+ scribed.

Calculations based upon' experience have are similar and are each attached to the similar thermostatic expansion valves IS. The distribu tors and their valves are preferably of the type shown by the U. S. Patent No. Re. 20,964 to Harry E. Morton.

' In operation, when serving as an air cooler, it is intended that the air to be cooled, enter the shown that in an evaporatorof. the type iuu's-- trated,"the suction temperature of the refriger ant should ,normally be about 40 F., with the evaporator operating at mid capac'ity, with eighty tubes service. Thenif the temperature of the gas rises above 40 F. to say 43 F., less surface is required, and proper operation may be had with only seventytubes. If on the other hand, the suction temperature falls below 40 same side of the electric source is connected by the wires and 3|, and by the. branch wires 32, 33, 34, and to one of the two terminals of each of the'electrical solenoids operating the valves 23, I9, ll'and 2| respectively.

Imbeddedin the stem of the thermomewr 25 are the'contact 31 at the F. division, and the contact 38 at the 43 F. division. -When the suction temperature is at 40 or between 40.and 43, the relayindicated' generally by 39 is energized to close. contacts, closingthe circuits energizing the solenoids ofthe valves l9. and 2| and opening the circuitsenergizing: other valves with the result that the distributors B and C serve eighty tubes of the evaporator 5. If the suction temperature falls bGIOWAQ F., the energizing circuits of the solenoids, of the valves l9 and 2| are opened and the energizing circuits of the valves l1 and H) are closed, causing-the distributorsAand: B to serve ninety tubes. If on the other hand, the suction temperature goes up to 43 F. the relay indicated generally by 46 is energized, causingthe relay 39-to become deenergized, the solenoids of the valves I1. and I9 to become deenergized and the solenoids of the valves 2| and 23 tobecome energized, causing I the distributors'C and D=to serve seventy tubes.

1 The. relay 4|! contains the, control solenoid 41 which is included in the electric circuit including the Wire 48, thethermometer contactc38, the wire 49, the electric source 36, the wires 3|land 39, and the thermometerbulb 28, When the suctionternperature reaches 43 thiscircuit is closed, and the solenoid 41 is energized to pull up its armature causing it to strike the contacts 5| and 52. This closes one circuit including the armature '56, the wire53, theeiectric 4 source-36, the wires 30, 3| and 35, the solenoid of the valve' 2|, the wires 54 and 55, and the contact 5| causing the solenoid of the valve 2| to z open-the valve to permitthe distributor C to serve thirty-five tubes ofthe evaporator 5. At

the same time, the circuit including thev armature 50, the wire 53, the electric source36, the wires '30,"3| and 32, the solenoid of the'v'alve 23, the. wire, 56 and the contact 52," is closed causing the solenoid of the valve 23 to. open this valveand to permit the. distributor'D'to serve the insulated armature 45 and separates the armature 45 from the contacts 44. This opens the circuitconnecting the relay 39 to the electricsource 36 andprevents the solenoids of the otherwalves l1 and' I9 from being energized through operation of the relay 39.

gized and the armature 45 strikes the contacts a 44. The circuit including the thermometer con- The bulb 2B of the thermometer 2f is connected by the wire 29 to the wire 30' and to one side of the electric source"36,." The jg tact 31, the wire 42, the solenoid 4|, the wires 51 and43, the contacts 44, the armature 45, the wire 46, the electric source 36, the wires 30 and t 29, andthe thermometer bulb 28, isclosed causing 5 the solenoid 4| to pull up its armature 5B and strike the contacts 59 and 60. This causes the closing of one circuit including the armature 58, the wires fil and 43, the contacts 44, the armature 45, the wire 46, the electric source 36-,"the wires'fiil, 3|" and 35, the solenoid of the 'valve 2|fthewires 54 and 62, and the contact 66; This causes the solenoid of the valve 2| to become energized to open the valve and to cause the distributor C to serve thirty-five tubes of the evaporator, 5. At the same time, a second circuit including the armature 58, the wires 6| and 43, the contacts 44, the armature 45, the wire 46, the electric source 36, the wires 30, 3| and 33, thesolenoidof the valve IS, the wire-63 and the contact 69, causingrthesolenoid of the valve l9 to become energized and the valveto open to cause the distributor Bto serve. 45 tubes of the evaporator 5. At this time, when the suction temperature is between 40 F- and 43 F.-, the distributors B and Cl serve a total of eighty tubes of the evaporator. l I When the suction temperature falls below 40 F., the above described circuit of the solenoid is energized, its armature 58 is'released, the last two described circuits including the contacts 59 and 60 are opened causing the solenoids of the valves I9 and 2| to become deenergized causing these valves to close. p

The armature 58 at this time strikes the contacts'64 and 65. This causes the completion of a circuitincluding the armature 56, the wires 6| and 43, the contacts 44, the armature 45, the wire 46, the electric source 36,'the wires 30, 3| and '33, the solenoid of the valve. |9,the wire '63 and the contact 64 causing the solenoid of the valve l9 to become energized to open the valve and causing the distributor B to serve forty-five tubes of the evaporator- 5. r At the same time, anothercircuit including i the armature 45, the wire'46, the electric source 36, the wires 39', 3| and 34, the solenoid of the valve ll, the wire 66 and the Contact is closed causing the solenoid of the valve I to become energized toopen the valve" and causing the distributor A'to serve the other forty-five tubes of the evaporator. Thus for suction temperatures below 40 F., the full ninety tubes of the evaporator are placed in service. v

The suction tube 25 contains the usualjthermostatic elements 61 connected by the tubes 68 in. dicated by the. dash-dot lines on. the drawing, to the thermostatic expansion valves l6 for controlling as shown by said Morton patent, the rate of flow-of the refrigerant. 60; Regardless of whether the evaporator is operating at maximum capacity, mid-capacity or minimum capacity, the effective air cooling tubes extend in multiple across the entire face of the 5 air stream being cooled, so that the effect is the same as if three separate, independent evaporators were provided.

While an evaporator adjustable to provide three surface areas has beendescribedtwo or more than three surfaceareas could be provided. In the claims the term tubes does not refer to the refrigerant conduits running from the refrigerant distributor tubes to the header, but

stantially parallel tubes such as the tubes 6, with refers to'separate, transversely extending, sub

adjacent tubes being interconnected at their ends as by the return bends I.

While one embodiment of the invention has been described for the purpose of illustration, it

should be understood that other apparatus and arrangements of apparatus may be suggested by those skilled in the art without departure from the essence of the invention.

What is claimed is:

1. An air cooler comprising a plurality of rows of tubes, each row containing a plurality of tubes, means including a plurality of distributors connected to the tubes of said rows at one end thereof and another plurality of distributors connected to tubes of said rows between the ends thereof for supplying refrigerant to said tubes, means including a plurality of Valves for supplying refrigerant to said distributors, and means for selectively adjusting said valves for varying the number of said tubes supplied with refrigerant.

2. An air cooler comprising a plurality of rows of tubes, each row containing a plurality of tubes, means including a plurality of refrigerant distributors for supplying all of said tubes with refrigerant, means including a second plurality of refrigerant distributors for supplying a portion of said tubes with refrigerant, means including Valves for supplying refrigerant to said distributors, and means including means responsive to changes in the temperature of the refrigerant leaving said cooler for selectively adjusting said Valves for supplying refrigerant to all of said tubes or to a portion of said tubes.

' tion of said tubes, means including a plurality of valves for supplying refrigerant to said distributors, and means including means responsive to changes in the temperature of the refrigerant leaving said rows for selectively adjusting said valves for varying the number of said tubes supplied with refrigerant.

4. An air cooler comprising a plurality of rows of tubes, each row containing a plurality of tubes, means including a plurality of distributors connected to the tubes of said rows at one end thereof and other distributors connected to the tubes of said rows between the ends thereof for supplying refrigerant to said tubes, means including a plurality of valves for supplying refrigerant to said distributors, and means including means responsive to changes in the temperature of the refrigerant leaving said rows for selectively adjusting said valves for varying the number of said tubes supplied with refrigerant.

5. An air cooler comprising a plurality of rows of tubes, each row containing a plurality of tubes, refrigerant distributor means connected to tubes of said rows at one end thereof, refrigerant distributor means connected to, tubes of said rows between the ends thereof, means including valves connected to said means for supplying refrigerant thereto, and means for selectivelyadjusting said valves for varying the number of tubes supplied with refrigerant.

, ,6. An air cooler comprising a plurality of rows of tubes, each row containing a plurality of tubes,

refrigerant distributor means connected to tubes of said rows at one end thereof, refrigerant distributor means connected to tubes of said rows between the ends thereof, means including valves connected to said means for supplying refrigerant thereto, and means including means responsive to the changes in temperature of the refrigerant leaving said cooler for selectively adjusting said valves for varying the number of tubes supplied with refrigerant.

7. An air cooler comprising a plurality of conduits, each extending from one end of said cooler to the other and including an inlet and an outlet; a refrigerant distributor connected to the inlet of each conduit; a second distributor connected to each conduit between the inlet and the outlet thereof; a valve arranged to control the flow of refrigerant through the first distributor; a second valve arranged to control the flow of refrigerant through the second distributor; and means, responsive to a condition brought about by the evaporation of refrigerant in said conduits, for operating said valves to permit the flow of refrigerant selectively through one or the other of said distributors.

8. An air cooler comprising a plurality of conduits, each'extending from one end of said cooler to the other and including an inlet and an outlet; a refrigerant distributor connected to the inlet of each conduit; a second distributor connected to each conduit between the inlet and the outlet thereof; valve means arranged to control the flow of refrigerant through at least one of the distributors, and means responsive to a condition brought about by the evaporation of refrigerant in said conduits for operating said valve means to prevent the flow of refrigerant through said one of the distributors.

9. In apparatus of the character described, in combination, conduit means forming a heat exchanger, said means having an inlet and an outlet, means for admitting heat exchange medium to said conduit means at the inlet thereof, means for admitting heat exchange medium to said conduit means at a point intermediate the inlet and outlet thereof, and means controlling inlet and outlet thereof, means controlling the admission of heat exchange medium at the inlet of said conduit means and at said intermediate point, and means responsive to temperature of heat exchange medium at the outlet of the heat exchanger controlling the total supply of heat exchange medium to the heat exchanger.

11. In apparatus of the character described, in combination, heat exchange means having a plurality of passes, means forming a distributor,

means connecting said distributor to a plurality of said passes, means forming a second distributor, meansconnecting said second distributor to intermediate points of a plurality of said passes, means controlling the admission of heat exchange medium to said distributors, and means responsive to temperature of heat exchange medium at the outlet of the heat exchanger for controlling said last mentioned means.

SAMUEL M. ANDERSON, 

